Bring a large pot of salted water to a boil. This will be used to cook the pasta shells later.
Heat a drizzle of olive oil in a saute pan over medium/high heat. Add in the sausage and cook for about five minutes, making sure to continuously mix and break apart the sausage into smaller pieces. Mix in the garlic and onion and cook for another one to two minutes. Mix in the pepper and then lower the heat and continue to cook for another five minutes. Remove from the pan and set aside to cool down.
Meanwhile, heat up the tomato sauce over medium/low heat. Preheat the oven to 400 degrees F.
Begin cooking the pasta shells in the pot of the boiling salted water for about four to five minutes less than the cooking time found on the package. Drain and rinse in cool water to stop from cooking. Set aside.
Add half of the pecorino cheese and half of the mozzarella cheese to the sausage and peppers and mix together.
To assemble the sausage and peppers stuffed shells, coat the bottom of a baking dish with some of the tomato sauce. Working with one shell at a time, scoop some of the sausage and peppers mixture into the shells. Place onto the baking dish. Once all of the shells are stuffed, scoop a tablespoon of tomato sauce over each shell. If you prefer a lot of sauce, feel free to add more sauce. Place the baking dish into the oven and bake for 15 minutes.
Remove the baking dish from the oven and sprinkle the remaining mozzarella cheese and pecorino cheese over the stuffed shells. Place back into the oven and bake for another five minutes or until the cheese has melted.
Remove from the oven. Sprinkle some fresh parsley on top and serve. Enjoy! Salute and cin cin!